What could cause a lot of pressure on the coolant system? there is no coolant on the oil and there is no oil in the coolant

the pressure is too high that leak coolant from the cap of the coolant reservoir tank, which I have replaced by a new one and also the cap, and still do the same thing.

the thermostat is new and is working.

thank you.

 

If the headgasket is leaking it can force combustion gasses into the coolant passages....causing excess pressure...same for cracks is some locations.
Typically a test can be done to determine if exaust gasses are present or the coolant tank is pressured with a special cap/and adapter....and you see if the pressure drops...

But the question is, how full were you keeping the tank?
About HALF FULL ...to the seam on the side, just so the baffles are covered is enough...
Remember, the tank is an EXPANSION TANK, so there must be room for the coolant to expand as it gets hot.

 

since the problem always keep it to the bafless level..and w/ the open cap I can see the return coolant circulating on the hose of the top of the tank.. the coolant return to the tank.. and is circulation.

 

water pump was replaced, water flange replaced, replace thermostat , was serviced the radiator, tank reservoir filled to bellow the mark, flush the system till leak coolant from the upper screw bleeder hose. if car idle wont leak water from the tank cap, but if regular drive or accelerate will place a lot of presure on cooling system and make the tank cap leak steam and coolant..please help

 

You probably have a leak somewhere. If the system isn't able to hold 14 PSI it isn't cooling properly and thus you're having coolant expanding into and out of the tank when the car gets hot.

I just had to replace the spring clamps on my steel oil cooler lines with worm clamps due to them having a ridiculously small leak and causing the same problem. Been 2 days now with zero issues and coolant staying where it needs to.

Pressure test the system, find a coolant pressure tester and let the car sit with pressure on the system for 10 minutes. If you lose substantial pressure (2+ PSI) you have a leak and need to find it.

 

Hi,
My hoses seem to have a very small leak too.
What size hose hose clamps do I need?
Thanks